This invention relates to the area of precision machining, and in particular the automated manufacturing or re-manufacturing of tools by grinding work pieces.
In the art, tool making machines that implement a fully automatic production process without operator intervention for extended periods of time are known. Work pieces are loaded by a loader into, for example, a grinding machine and precisely ground in accordance with prescribed measurements to make finished tools. Particular attention is paid to the cutting geometries, i.e., the precision of the grinding treatment of the cutting edges and of the surfaces adjacent to the cutting edges of the tools (e.g., free surfaces or chip surfaces).
A German patent, DE 4242506 Cp2, describes a numerically controlled grinding machine for machining work pieces, preferably metal tools. The grinding machine has a grinding head, which may be systematically adjusted by linear translations along and rotations about several axes. The machine also has a similarly adjustable work piece receptacle. A control system, in accordance with a prescribed program, directs drives to adjust the work piece receptacle and the grinding head while grinding work pieces to make tools such as, drills, millers and other chip removing tools.
Ever more stringent quality requirements are leading to demanding tolerances in the manufacture of tools. For maintaining a constant production quality it is, therefore, advantageous to compensate for the influence of interfering factors, such as temperature changes, wear of the grinding disk and the imprecision in the mechanical system. To this end the production process is interrupted in order to check the quality of the tools being produced by external measurements. In case of excessive wear of a grinding disk, a grinding machine must be readjusted in order to stay within an acceptable range. Needless to say, production interruptions and manual readjustments hamper fully automatic operations.
In light of the foregoing discussion, it is desirable to create a device and a process for the metal-removing treatment of work pieces, in particular a grinding machine, with which an interruption-free operation is possible.
In accordance with the invention, a grinding machine or other processing machine is integrated with a sensor in the form of a measuring arrangement, which considerably simplifies the monitoring of the process with the detection of, possibly, all the relevant quality parameters. Using the integrated system, the tool being ground into a prescribed shape can be checked during and after the treatment process. The integration of the measuring arrangement with the grinding machine makes possible a consistently high production quality, reduces the rate of rejected parts and effectively eliminates the need for manual checking by an operator.
In a preferred embodiment, the sensor is in the form of an optical measuring arrangement. In the case of an optical measuring arrangement it is possible to use, both, glancing-light or transillumination, and direct incident light based techniques. An incident-light illumination permits the recording of inner measurements, such as, for example, chip angle or chip-space depth and the radial position. In contrast, transmitted sight is well suited for the detection of sharp edges such as blade edges. Furthermore, a CCD camera has been notably successful in the context of precise measurements on the outer contour of sharp-edged tools. Consequently, it is possible to replace mechanical sensors with optical sensors and electronic image processing while tracking processing of a work piece.
In accordance with a further aspect of the invention, to permit a high incident light intensity, a mobile illuminating unit, adjustable with respect to the measuring arrangement, is used. If an incident light measurement is to be carried out, the illuminating unit is moved closer to the work piece surface by means of an adjusting arrangement. In this manner, the desired high light intensity may be variably achieved.
To determine whether further processing of the work piece is required, or whether the grinding process can be terminated a final measurement from the sensors is utilized. In the event that a fault cannot be corrected by a renewed working, the work piece is automatically recognized as waste and rejected. In subsequent processing, the grinding program is readjusted to avoid further rejects.
The measurements carried out during the process make possible the detection of a potential fault prior to the production of rejects. If, for example, temperature variations or wear on the grinding disks result in measurement changes, the production process can be altered to stay within the prescribed tolerance. This is made possible by means of a program, executed by a control arrangement, to monitor trends on features approaching. tolerance limits and perform readjustments of the grinding parameters.